In recent years, demand for a centralized monitoring system which monitors multiple devices which are spread out over many remote locations has increased. There is also a demand for maintenance operations which are more efficient.
A conventional structure of the centralized monitoring system will be explained, based on FIGS. 9 and 10.
FIG. 9 is a diagram of a system structure of a general centralized monitoring system. In FIG. 9, reference numerals 911 through 932 designate devices to be monitored. For example, they could be transmission devices in a transmission system.
The multiple devices 911 through 932 are arranged in multiple groups. For example, in FIG. 9, the devices 911 and 912 belong to one group, or one region, and the condition of these devices 911 and 912 is monitored by a corresponding intermediate monitoring device 91.
In the same way, the devices 921 and 922 are monitored by an intermediate monitoring device 92, and the devices 931 and 932 are monitored by an intermediate monitoring device 93.
Further, information from the devices 911 through 932 to be monitored is collected and monitored by the centralized monitoring device 90 via the intermediate monitoring devices 91, 92 and 93.
In such a general centralized monitoring system, the information from the devices 911 through 932 is sent to the corresponding intermediate monitoring devices 91 through 93 in the form of a message such as a telegram or the like. The messages sent from the devices 911 through 932 are received via the intermediate monitoring devices 91 through 93 in the centralized monitoring device 90. The messages specify the device in which the fault is occurring and the details of the fault.
The centralized monitoring device 90 has a storage device which stores a finite set of the faults in a time base, when the messages from the monitored devices are received. Restoration times are also recorded.
FIG. 10 shows the above-described operation. In FIG. 10, reference numerals 100 through 103 are messages which include the information of the fault stored in the time base in the order of the fault occurrence.
In FIG. 10, the message 100 indicates the occurrence of a fault A, which happens at the earliest time, and the message 101 indicates the restoration of a fault B, which is sent after that. Similarly, the message 102 records the occurrence of a fault C, which is received and recorded at a later time. Further, with the message 103 the restoration of the fault A is received and stored.
A pointer 104 is provided in the storage device. This pointer marks the latest data. That is, the message 103 for indicating the restoration of the fault A is marked by the pointer 104 in FIG. 10.
In the monitoring indication system in the conventional centralized monitoring system, only the latest data marked by the pointer is indicated, when the operator requests that faults be indicated.
As described above, only a single fault can be monitored effectively in the conventional system. However, there are problems in the conventional system as follows. One problem is that only the latest data marked by the pointer is indicated, as shown in FIG. 10, although the information required by the person in charge of maintenance includes the fault which is occurring currently. Accordingly, where the fault stored first has already been restored, the fault indication of the pointer is meaningless.
Another problem is that information about previous faults cannot be reviewed because the pointer only marks the latest data. It is possible to store indications of past faults when the messages stored in the storage circuit are later checked. However, it takes too much time to find indications of past faults because bulky information must be checked.
Further, the storage device has limited capacity, so the device can only store a finite set of information, and information relating to the faults is limited.
Accordingly, it is an object of the present invention to provide a centralized monitoring system to solve these problems with conventional systems.